Desulphurizing hydrocarbon distillates



Oct. 31, 1944. w. A. PROELL ET AL DESULPHURIZING HYDROCARBON DISTILLATES Filed Feb. 28, 1942 Patented Oct. 3l, 1944 i 2,361,651 nasuu'numzmd mmaocAnBoN msrmmras Wayne A. BroelL Chicago, lll., and AFrank K. Ovitz, Whiting, Ind., asllgnorl to Standard Oil Company, Chicago, Ill., a corporation of Indi- 'Application Fermn 2s, 1942, serial Nc. 432,876

11 claims. (c1. 19o-2s) This invention relates to a process of sweetening and desulphurizing petroleum napthas.` gasoline, kerosene and similar lpetroleum distillates contaminated with sulphur compounds. ,It relates more particularly to the catalytic treatment of petroleum distillates in the vapor phase to remove therefrom sulphur compounds aiiecting the Patterson-Sargent test hereinafter described. The process is applicable to cracked stocks as well as straight-run stocks. v One object of the invention is to renne napthas and petroleum distillas by contact catalysts in a manner to produce larger yields of satisfactory corrosion-free products than heretofore obtainable. Another object of the'invention is to provide a catalyst for effecting the sweetening of sour petroleum distillates to a degree suiiicient to have the product pass the Patterson-Sargent test. Still another object is to provide a desulphurizing catalyst having longer active life than possessed by catalysts heretofore employed.

The invention is illustrated by a drawing which shows diagrammatically an apparatus for` conltasting naptha 4vapors' with contact catalysts made in accordance with this invention.

' Referring to the drawing, the feed stock which .may be a petroleum naptha/or otherlight petroleum distillate may be charged by line loto heater il wherein it is vaporized and heated to the temperature desired for the reaction or .a little above that temperature, to allow for heat losses Il and condenser 20, the vapors being conducted ltoitbyline I9.

where the distillate is allowed to now'upwardly through a bath of caustic solution. The washed distiliate is withdrawn by line 21 leading to treated distillate outlet 24. l i

After the catalyst in I3 has become exhausted, it may be withdrawn through Ib and replaced through Il. If desired, however, it may be re- `generated in place by closing the vapor inlet line in the reaction chamber. The vapors are thence A foraminous plate or screen I6 may support the granular catalyst in a bed. Air or oxygen may be introduced at the desired rate by line I1.

` If desired, the air may be introduced into the vapors in line I2. Condensates which may form f y 'in the reaction chamber, especially when starting operations with a cold` catalyst, are withdrawn by valved outlet I8. f

The treated hydrocarbon vapors pass'by vapor line I9 to condenser 2b and thence to receiver 2| 'from which spentigases, nitrogen, etc., are with-l drawn by vapor line 22. If it is desired to further fractionate the distillate, this may be done 'by I2 and transfer line I0. Heated air supplied by line'Il may then be employed to regenerate the catalyst. the spent-regeneration gases being discharged by valved line 28. After regeneration is complete the catalyst may be allowed to cool to the desired reaction temperature, for example,

'by passing cold air therethrough; vent 2l may be closed and the sweetening operation continued as before.

Previously, the testing of'napthas generally required that they be made to pass the so-called "doctor test which involves shaking a sample of the naptha with a solution of sodium plumbite in alkali and noting the formation of an insoluble lead mercaptide which appeared either as).` ooioration in the naptha or as a rag at theinterface between the naptha and the water solution. For general purposes, this test proved eatil'factory but it was later found that the test suillciently stringent for napthas intended for special uses, particularly inlthe manufacture of paints, lacquers and varnlshes. Small amounts of corrosive sulphur compounds in such nllbu were found quite harmful to pigments an'd accordingly more stringent tests were devised to de. tect the presence of these undesirable corrosive l sulphur compounds. It was also found that traces of. organic disulphides in motor fuels low- ',ered the knockrating and susceptibility to tctra ethyl lead. v Une test which .has been found quite sensitive for detecting minuteV amounts of corronve au1- employing a fractlonating tower between reactor 5o phur compounds is thsPatterson-Sargent-rtrlp test which is carried out ,in the following manner: A strip of polished copper measuring 1A. inch by 1?/2 inches is placed in a standard A. S. T. M. distillation flask and 100 m1. of the naptha in question is added to the flask. The naptha is then distilled according to the standard A. S. T. M. distillation procedure until the end pointis reached. The copper strip is then removed from the ask and cooled rapidly by immersing in a coolant such as cold naptha or acetone to avoid contact with air which would cause discoloration. The corrosive condition of the naptha sample is determined by the color of the copper strip. AThe naptha is rated No. lor perfect if there is no color change; No. 2 if the strip has a slight purplish tinge; No. 3 if the strip khas the color of brass; No. 4 if the strip is iridescent or grayish in appearance, and No. 5 if the strip is sooty black.

Petroleum distillates sweetened by the earlier methods with doctor solution, for example, will not satisfactorily pass the Patterson test but invariably give gray or black strips. Accordingly, diierent refining methods must be resorted to in order to produce salable products which -will meet this stringent specication. One of the methods found effective for this purpose is one wherein the nap' la vapors are brought into contact with copper oxide or other copper compounds, preferably employed on a supporting material. The

effectiveness of the copper lcompound. has been found to vary considerably with the character of the supporting material with which it is associated'such as .the clays, bentonite, fullers earth, etc., employed heretofore.

The yield of sweetened naptha obtain-able by this process is very greatly increased by simultaneously introducing oxygen or air into the catalyst bed with the naptha vapors. The reaction involved in the process appears to be an oxidation of merc-aptans, sulphides and disulphides to sulphur dioxide by the action of the copper catalyst in the `presence of the oxygen. The amount of. naptha lost in' the process is small, usually less than 1%.

We have now discovered that the yields obtainable by this process can be very greatly increased by using a catalyst in which the copper compound is associated with a compound, particularly with oxides, hydroxides or carbonates of metals found in group II of the periodic system, more particularly magnesium, calcium, zinc, and

` barium. Sulphates and phosphates may also be used but are less preferred. The life of these catalysts isl very much longer than the life of catalysts heretofore employed as indicated by the yield of sweetened distillate. Thus, a catalyst composed of copper oxide and magnesium carbonate gave, for one ton of catalyst, a yield of 4500 barrels of oleum spirits having a perfect Patterson-Sargent test and an additionalyield of 6000 barrels' of product testing No. 2 by the Patterson-Sargent test which would be quite satisfactory for almost all present commercial speciiications. vIn comparison, copper oxide catalysts heretofore employed yielded only a few hundred barrels per ton of naptha ofsatisfactory corrosive-characteristics. Furthermore, many of the catalysts heretofore employed were found incapable,;.;of producing any product whatever which satisfactorily passedthe Patterson-Sargent test. Thus for example, copper oxide on chromium oxide gave a sour product while copper oxide on bauxite gave a verylow yield of sweetened product. only 200 barrels per ton.

charged. The amount of air In carrying out our process we prefer to employ the following procedure: The naptha is vaporized preferably in a pipe heater in a continuous stream and the vapor is passed through a bed of catalyst at a temperature within the range of about 350 to 600 F. Higher temperaturesthan these are generally undesirable because of excessive oxidation of the hydrocarbons with the formation of aldehydes or other undesirable'byproducts. Atmospheric or slightly superatmospheric pressures, of the order of 25-to 50 pounds per square inch, are satisfactory. A stream of air is introduced with the catalyst at the rate of about 1/2 pound of air per barrel of naptha employed will vary considerably, depending upon the character of the naptha and the amount of sulphur compounds to be removed from it. Thus with Mid-Continent naptha containing about 0.03% sulphur and about 0.01% mercaptan sulphur, the minimum amount of air is about 0.3 pound per barrel of naptha. In general, the amount of air employed will be about 116 to 10% by weight of the oil treated.

In addition to the group II metal oxides, hydroxides and carbonates, We may incorporate in our catalyst various plastic materials having the property of increasing the mechanical strength and hardness of the catalyst. Examples of such materials are the adsorbent earths such as bentonite, Wilkinite and montmorillonite clays, silicaalumina hydrogel, etc. The amount of these materials employed may vary considerably. generally in the range of about to A typical catalyst made in this manner contained 18% of copper sulphate, 41% of magnesium carbonate, and 41% of Wilkinite. It was much stronger than the oatalyst'without the Wilkinite while exhibiting an equal or greater desulphurizing activity.

As a specific example of the preparation of our catalyst the following illustration is presented.`

To 1 kilogram of granular Attapulgus clay there was added 50 grams of powdered calcium oxide and grams of powdered magnesium oxide. After mixing dry, suicient water was stirred in to make a heavy paste. A solution of copper sulphate was preparedby dissolving 200 grams of the salt, CuSO45HzO, in hot water and this solution was slowly added to the paste with stirring.

lAfter mixing to a homogeneous mass the paste was formed into lumps and allowed to dry. The dry lumps were crushed and screened to a size of 14 to 28 mesh. lThe catalyst was then ignited for 15"minutes at a moderate red heat, about 1000 F. On cooling the catalyst was ready for use. 'If desired, the paste may be washed with ywater before drying to remove soluble sulphates or other salts but this step is not necessary for the production of active catalysts.

In another example, parts of Wilkinte was made into a very thick paste with 60 parts of copper sulphate vdissolved in an excess of water. To

the mixture was added 100 parts of magnesium carbonate and 250 parts of diatomaceous earth, mixed together with suflicient water to form a -stiif mud. The two pastes were then mixed and kneaded thoroughly. Fifty (50) parts of additional dry Wilkinite clay was added. The mixture was further kneaded untilhomogeneous. The catalyst was dried, crushed, sized and ignited as previously. The product was very active and posr'sessed considerable mechanical strength as well as a high porosity. It was used directly without pelleting or extrusion.

Gasoline sweetened by our catalytic process is characterized by kan improved knock rating when aachen compared with gasoline sweetened by ordinary methods such as the "doctor method as the following results will indicate:l

could be varied within the range of' about 25 to 150 barrels per hour per ton of catalyst and produce a sweet product. In general, feed rates at about themiddie of this range, 50 to 100 barrels per hour-per ton, appear to be advantageous from the standpoint of producing a consistently satisfactory product. With certain very active catalysts, such as CuO and MgOa, feed rates as high as 260 barrels per hour per ton were attained. but the catalyst was too soft for practical use. The following data show the results of one series of tests in which the feed rate .was varied with a typical CuO-MgO-CaO catalyst:

The effect of temperature in the operation of our process was carefully studied and it was found, that in the case of the particular Mid-Continent naptha employed, at temperatures below 400 F., the product obtained was not satisfactorily sweetened when tested by the Patterson-Sargent test. In this case, it was found desirable to opcrate above 440 F. Above 440 F. the temperature was substantially` without effect on the desulphurization ,although excessive temperatures o appreciably above 600 F. result in the formation of undesirable oxidation products as previously indicated.

The following data were obtained when feeding a sour naptha stock at the rate of 116 barrels per hour per ton ofcatalyst. T he catalyst employed was made by mixing a solution of copper sulphate with a` paste of magnesium carbonate (7%), calcium oxide (3.7%) and Attapulgus clay (74%) drying, crushing and sieving to pass 14 mesh and be retained by 28 mesh, and igniting to about 900 F. Air was simultaneously injected into the catalyst during the tests at the rate of 1.4 volumes of air per volume of liquid naptha-charged.

Temperatme, F. nfp: Puig-toon 0. 045 Grey. 0.0%

0.020 Trace 'urplm 0.020 05 perfect. 0.025 Perfect. 0.038 D0, (030 Do. 0- Do.

im the above tests the naptha was obtained sweet directly from the condenser after passing through the catalyst when the temperature was within the range of 440 F.. to 500 F. At temperatures V A straight run heavy naptha from Mid-Con- 15 I Doctor Patterson tinent crude gave the following results: Feed rate, brrelspertnper hour test Sargent wat Knock rating A. s. 4c sweet-.. Perfect.

T. M. 68 -..do Do.

s? "gom" su ilio'urpx 0--- 8. Docu, cammi- 20 im dn rrgfle.) sweetened cally 116 -..do P ect.

.. 130 -.do Slight purple. 141i Sour'. Iridescent grey.

Gasoline unleaded l27. 3 29. 2 ggg@ sglie gglgg Tests made to'determine the amount of air ref "E e 25 quired for carrying out the process indicate that stocks as little as 0.5 volume of air per volume of I stock maybe employed. Excess air does no particularf harm if kept sufficiently low to avoid explosion hazards. To obtain minimum losses. however, the correct amount of air should be used.

The following data show the 'results obtained in the sweetening of oleum spirits which is a naptha fraction from Mid-Continent crude oil having the following boiling range:

0F Initial 304 10% '321 50% ,349" 90% 392 End point 427 The stock was charged to the catalyst at the rateV Y of 116 barrels per hour per ton at a temperature we and 1n general that cne'nrcor our catalyst may be' increased by reducing the feed rate, which v in fact increases the-time of contact between the oil vapor and catalyst. However, for practical purposes it is not generallyl desirable to reduce the feed rate below about 25 to `50 barrels per hour` per ton, especially when treating low sulphur napthas which can be sweetened at far higher rates with fresh catalyst. When the catalyst fails Vto produce a satisfactory product at thisrate as indicated by the Patterson-Sargent test, it lis desirahle to replace the catalyst or regenerate it.`

4- I Regeneration may be accomplished by oxidation in situ or in a separate operation. Igniting the catalyst in the presenceof air for one hour at a temperature of about 1000 F. has been found to restore catalytic activity. In general, we prefer to pass a current of heated air through the catalyst bed maintaining the temperature of the catalyst within the range of about 800 to 1200 F., thereby burning oi carbonaceous matter and oxidizing metallic sulphides.

In preparing our catalysts we prefer to use ent, the yield considerably exceeded 8300 barrels per t0n.

In preparing our catalyst we may mix copper oxide or other insoluble copper salt such as the hydroxide or carbonate directly with the group II metal compound and this may be done by grinding the iinely powdered copper compound with the group 1I metal oxide, hydroxide or carbonate in a ball mill, preferably while wet. Clay may be added .to the mixture at this time. The wet mixture is then dried-and crushed to size or it may be extruded or ground and pelleted. Other insoluble copper compounds may be employed with this method if desired, for example, copper oxalate or copper resinate. In the case where organic copper compounds are employed,it is desirable to ignite the catalyst in the presence of 2o` mum yield of sweet products was 1000 barrels per ton whereas with the group II metal oxides preslow. Where the term barrel is used in this specication it refers to the standard barrel of e2 U. S. gallons. v

We claim:

l. The process of sweetenlng and desulphurizing sour hydrocarbon distillates which comprises contacting the vapors of said distiliates in the presence of oxygen with a catalyst comprised of copper oxide in-combination with at least an equal amount of an oxide, hydroxide or carbonate of a metal selected from the class consisting of magnesium, ycalcium and barium. y 2. The process of sweetening and desulphurizingI petroleum distillates which comprises contacting the vapors of said distillates in the presence of oxygen with a catalyst comprised oi a mixture of copper oxide, calcium oxide and magnesium oxide.

3. The process of claim 2 wherein the proportion of copper oxide in said catalyst mixture is about 1/2 to 116 of the calcium and magnesium oxides.

li. The process of sweetening and desulphurizing naphthas comprising contacting the vapors oi" said naphthas in the presence of oxygen at a temperature of about 400 to 600' F. with a catalyst prepared from-an intimate mixture of cop- `per oxide and at least an equal amount of an 0xide of a metal selected from the class consisting of magnesium, calcium and barium.

5. The process of claim 4 wherein the temperature is maintained at about 450 to 550 F.

6. The process of sweetening and desulphurizing petroleum dist.llates which comprises contacting the vapors of said distillates in the presence of air with a solid contact catalyst at a rate air to decompose and remove organic material o before using the catalyst.

In general, we prefer to add soluble copper salts in water solution to the group II metal compound with or without the addition of clays as hereinbefore indicated. Copper sulphate, copper nitrate and copper "acetate are examples of readily available copper salts suitablefor making the catalyst. In general, our data indicate chloride ions should be avoided. The amount of copper incorporated inour catalyst is preferably about l part of copper oxide to l to 10 parts Iof the group II metal oxide or oxide mixture.

The chemical reactions involved in our process are apparently quite complicated. Analyses of the eiiiuent gases indicate that oxidation is the principal reaction so that CO2 is the principal product with, sulphur dioxide occurring as the p principal sulphur compound removed from the hydrocarbon. The following results were obtained by treating oleum spirits with a catalyst made from copper oxide, calcium oxide and magnesium oxide deposited on Olmstead clay, employing about 1 volume of air per volume of stock treated.

Although we have described our invention with respect to certainy specific examples thereof, we intend that it be dened by the claims which folof about 25 to 250 barrels of distillate per hour per ton of catalyst, said catalystl being comprised of a mxture of copper oxide and at least an equalk amount of an oxide of a metal selected from the class consisting of magnesium, calcium and bari- '7. The process of sweetening and desulphurizing sour petroleum distillates to render them noncorrosive according to the Patterson-Sargent copper strip test which comprises contacting the vapors of said dlstillates in the presence of air with a solid catalyst consisting essentially of copyper oxide and at least an equal amount of magnesium oxide maintained at a temperature of about 400 to 600 F., the rate of contact of said distillate with said-catalyst being about 25 to 250 .barrels of liquid distillate per hour per ton of catalyst.

8. The process of sweetening and desulphurizing sour hydrocarbon distillates which comprises contacting the vapors of said distillates in the presence of oxygen with a catalyst comprised of copper oxide in combination with at least an equal amount of an oxide, hydroxide or carbonate of Aa metal selected from the class consisting of magnesium, calcium and barium, said catalystbeing supported on an adsorbent earth.

9. The `process of sweetening and desulphurizing petroleum distillates which comprises contacting the vapors of said distillates in the presence of oxygen with a catalyst comprised of a mixture oi copper oxide and at least an equal amount of calcium oxide.

10. The process of sweetening and desulphurizing petroleum distillates which comprises contacting the vapors of said distillates in the presence of oxygen with a catalyst comprised of a mixture of copper oxide and at least an equal amount of magnesium oxide.

2,sa1,e51 v 5 11. The process of renng sour petroleum distillates to make them perfectly sweet according to the Patterson-Sargent strip test which comprises contacting the vapors of said distillates at about 350 to 600 F. in the presence of air in the amount of about 0.1% to 10% by weight of the distilylate treated, with a solid catalyst composed of a mixture of copper oxide and at leastan equal amount of an oxide, hydroxide or carbonate of a metal selected from the class consisting o! magnesium, calcium and barium.

' WAYNE 1A. PROELL.

FRANK K. 'OVI'IZ 

